In recent years, a workpiece such as a silicon single crystal ingot is often sliced into a wafer shape by using a wire saw. In slicing using the wire saw, first, a workpiece W to be sliced is held by such a workpiece holder 100 as show in FIG. 7 which includes a workpiece plate 102 to hold the workpiece W through a pad plate 103 and a holder main body 104 to support the workpiece plate 102. Then, the workpiece holder 100 holding the workpiece W is attached to a wire saw, and the workpiece W is pressed against a wire row formed by winding a wire which reciprocatively travels in an axial direction around a plurality of grooved rollers, whereby the workpiece is sliced into a wafer shape (see, e.g., Patent Literature 1). As shown in a side view in FIG. 8, the wire saw slices the workpiece W in a perpendicular direction of the workpiece holder 100. Further, as shown in a top view in FIG. 8, each wire forming the wire row is substantially orthogonal to the workpiece holder 100.
Slicing of the workpiece such as a single crystal ingot is performed based on a crystal plane of the single crystal ingot. However, in general, there is a deviation between a central axis of a shape of a columnar ingot and a normal line (a crystal orientation axis) to the crystal plane. This deviation will now be briefly described with reference to FIG. 9. It is to be noted that, in this specification, of radial directions of a workpiece, a direction parallel to a surface of a workpiece plate to which a workpiece is bonded and fixed is defined as an x axis direction, and a direction vertical to the same is defined as a y axis direction. In an example shown in FIG. 9, the crystal orientation axis has a deviation Δx in the x axis direction and a deviation Δy in the y axis direction to a central axis of a shape of a single crystal ingot.
As methods for slicing a workpiece by using a wire saw, there are a method for matching a crystal plane of a single crystal ingot with a traveling direction of a wire and then performing slicing (just angle) and a method for setting a predetermined angle between the crystal plane and the traveling direction of the wire and then performing slicing (off-angle). In both the slicing methods, when the deviations of the crystal orientation axis are present, a direction of the single crystal ingot to the wire row must be corrected before starting slicing the single crystal ingot. To carry out correction of the deviations/setting of angles of the orientation of the single crystal ingot (which will be also referred to as orientation adjustment hereinafter), for example, the following method is known.
For example, in case of bonding and fixing the ingot to the workpiece plate of the workpiece holder through the pad plate, there is a method by which the ingot is rotated around the central axis of the ingot on the pad plate to adjust the crystal orientation in the y axis direction, and then an attaching angle of the ingot to workpiece holder (a tilt in the x axis direction to the workpiece plate) is changed to adjust the crystal orientation in the x axis direction. As described above, the orientation adjustment can be carried out by adjusting a rotating position and a bonding direction of the ingot to the workpiece holder. Furthermore, such a method for adjusting the crystal orientation before attaching the single crystal ingot to the wire saw is generally called an external setup manner.
Besides, there is also a method by using a wire saw including an orientation adjustment mechanism therein, a workpiece holder having a single crystal ingot attached thereto is set, and then the orientation adjustment is performed in the wire saw. Such a method for disposing the single crystal ingot to the wire saw and then performing the crystal orientation in the wire saw is generally called an internal setup manner.